Case report: Right vertebral and carotid artery anomalies with an aberrant right subclavian artery in two patients

Abnormal origins of the vertebral artery with supra-aortic vessel variants are exceedingly uncommon. Herein, we present two cases of the vertebral artery originating from the right common carotid artery associated with the right subclavian artery arising separately as the initial branch of the aortic arch, followed by the right common carotid artery. We reviewed the embryology of the anomalous origins of the vertebral and subclavian arteries. These variants can significantly affect surgical planning and cause severe clinical symptoms.


Introduction
Abnormal origins of the right vertebral artery (RVA) are uncommon, occurring at a rate of 0.18% in the general population (1).Right subclavian artery (RSCA) variants are primarily observed in vascular ring anomalies of the aortic arch, with incidence rates ranging from 0.5% to 2% (2).Therefore, RVA anomalies with an aberrant RSCA are extremely rare.To the best of our knowledge, an abnormal origin of the RVA associated with the RSCA arising as the first branch of the aortic arch has not been described in the literature (1,3).We present two cases of the RVA originating from the right common carotid artery (RCCA), associated with the RSCA arising separately as the initial branch of the aortic arch, followed by the RCCA.

Case reports Case 1
A 65 years-old woman presented with a history of acute severe headaches the previous year after an emotional trauma.She has no significant family or past medical history.Brain CT revealed a diffuse subarachnoid hemorrhage and a right posterior communicating aneurysm (PComA) was seen on CT angiogram.This patient was successfully treated with microsurgical clipping.An initial cerebral angiogram was performed for follow-up.Digital subtraction angiography (DSA) imaging demonstrated that the RVA arose from the RCCA and that the RSCA was the first branch arising from the aortic arch, followed by the RCCA (see Figure 1).A 60 years-old man with hypertension presented with a history of severe acute-onset headaches.Computed tomography angiography (CTA) of the head identified a left PComA aneurysm and a subarachnoid hemorrhage.In addition, arch CTA demonstrated that the RVA originated from the RCCA, part of the left subclavian artery (LSCA) was missing, the brachiocephalic trunk was absent, the RCCA and the RSCA had separate origins from the aortic arch, and the RSCA was the first branch to emerge, followed by the RCCA.DSA was performed and demonstrated that the LSCA had diverted blood from the RVA.A coiling procedure successfully treated the left PComA aneurysm and the patient's neurological condition was excellent at discharge.No intervention was performed for the LSCA, and the patient was managed with an antiplatelet regimen when necessary (see Figure 2).

Discussion
In a typical aortic arch anatomy, the vertebral arteries are conventionally identified as the primary branches of the subclavian arteries.The most common variation of the vertebral arteries is in the left vertebral artery, with an incidence rate of 2.4%-5.8%(3,4).In contrast, variations in the origin of the RVA are less common, with an incidence rate of 0.18% (1).If the RVA arises from the RCCA, its association with RSCA abnormalities also increases (5)(6)(7)(8).Although the embryology of abnormal RVA and RSCA is complex, understanding embryonic development and branching patterns can help explain these abnormalities.
During the early stages of embryonic development, the right ventral aorta forms the right common and brachiocephalic arteries.At the 7 mm stage, seven cervical intersegmental arteries (CIA) emerge on the aortic arch (9-11).At the 10-12 mm stage, the first to sixth CIAs anastomose longitudinally to form the VA (12).At the 14-17 mm stage, the horizontal segments of the first six CIAs degenerate and disappear, and the seventh CIA combined with the fourth aortic arch form the subclavian artery (5).Thus, the VA commonly arises from the subclavian artery, which is the largest and most proximal branch (Figure 3).
Nevertheless, incomplete involution of one of the first six CIAs leads to various anomalous origins of the VA (13).If the horizontal segments of the first or second CIA persist, an aberrant VA origin may develop in the external or internal carotid artery.If the third, fourth, or fifth CIA persist, the VA may originate from the RCCA.If the sixth CIA persists, an abnormal VA origin may arise from the aortic arch (Figure 4).
In addition, at the 40 mm stage of embryonic development, the remaining vessel of the right third aortic arch combines with the right half of the fourth ventral aorta to form the brachiocephalic trunk (BT).The possible cause of missing the BT is that the seventh CIA originates directly from the ascending aorta or that the right aortic arch partially degenerates, resulting in separate emergence of the RCCA and RSCA.The RSCA arises first, followed by the RCCA (Figure 4).
Although RVA and RSCA variations are only anatomical, and most are asymptomatic, it is essential to recognize these rare anomalies before surgery.When the RVA originates anomalously from the RCCA and its branches, injury to, or intraoperative blockage of, the corresponding carotid artery during surgery may

Conclusion
The RVA from an RCCA associated with an RSCA arising as the first branch, followed by the RCCA, is extremely rare.The embryology of abnormal RVA and RSCA is complex.Physicians should identify these abnormalities before surgery.

FIGURE 1 (
FIGURE 1 (A) Aortic arch angiogram showing the aberrant origin of the right subclavian artery and the right vertebral artery.(B) Illustration showing that the RVA originated from the RCCA, both the RCCA and the RSCA originated directly from the aortic arch, and the RSCA was the first branch, followed by the RCCA.LCCA, left common carotid artery; LSCA, left subclavian artery; RVA, right vertebral artery; RCCA, right common carotid artery; RSCA, right subclavian artery; LVA, left vertebral artery.

FIGURE 4
FIGURE 4 Schematic of the various anomalous origins of the VA.CIA, cervical intersegmental artery; R/LCCA, right/left common carotid artery; RICA, right internal carotid artery; LICA, left internal carotid artery; RECA, right external carotid artery; LECA, left external carotid artery.